Based on Alan Hunter's Inspector Gently book series, the new films will focus on veteran Scotland Yard detective George Gently (Martin Shaw) and his partner John Bacchus (Lee Ingleby) as they solve crimes in '60s Northumberland.
Peter Flannery and Mick Ford will co-write the four instalments.
"The joy of writing the Gently stories lies in the period and the place," said Flannery. "The place because it's where I grew up; the period for the same reason, plus it gives me a chance to write about a country on the cusp of change.
"Each issue I look at at the heart of a crime - abortion, sexuality, youth gangs, child abuse, race, terrorism - was seen differently in the early '60s compared to today. As L. P. Hartley said, 'The past is another country. They do things differently there'."
Holby City's Sharon Maughan will appear as an old flame of Gently who assists him in an investigation. Guest starring as suspects and victims in the first two films are Jill Halfpenny, Mark Williams, Paul Copley, Mary Jo Randle, Tracey Wilkinson and Brendan Coyle.